Detection Of Antibiotic Residues And Pesticide Residues Based On SERS Substrates Based On Porous Anodic Aluminum Oxide Membranes

With the improvement of the quality of life,food health and safety have gradually attracted people's attention.China is a large agricultural country.The development of agricultural industrialization brings up the more and more reliance on exogenous substances,such as pesticides and antibiotics,which allows a more sufficient and cheaper food supply.However,on the other hand,it brings about new issues,for instance food safety problems and environmental pollution,which influences the consumer's health,causes illness or even death.Therefore,the rapid detection of antibiotics and pesticide residues is an indispensable step.Surface enhanced Raman scattering?SERS?spectroscopy,with the features of being simple,convenient,fast and sensitive in detection,identifies the structure and chemical composition information of a substance at the molecular level using the spectral fingerprints of molecules based on their characteristic vibration.SERS now plays an important role in the food safety testing in food safety inspection.Meanwhile,the quality of the test results is judged in accordance with the SERS substrate.Hence,it is particularly important to fabricate a superior SERS substrate.Currently,aggregated silver/gold sols as SERS substrates have been widely used.Such substrate has high sensitivity,yet with stability and uniformity problems.Anodized aluminum oxide?AAO?is a nanomaterial with a honeycomb structure,which is beneficial to provide a more uniform SERS substrate array.Therefore,in this paper,AAO was used as a template,assembled with gold or silver nanoparticles to prepare a SERS substrate with good uniformity,sensitivity and stability,for rapid detection of trace antibiotics and pesticide residues in food.The specific work content is as follows:1.A two-dimensional uniform waffle-like SERS substrate?AAO/Ag SERS substrate?is prepared using in-situ reduction of silver nanoparticles?Ag NPs?with ascorbic acid?AA?direct on the AAO surface.The SERS substrate has good uniformity and repeatability?relative standard deviation,RSD=7.02%?.The limit of detection?LOD?for chloramphenicol is as low as 4×10^-99 mol?L^-1,and there is a good linear relationship between 10^-55 mol?L^-11 and 10^-88 mol?L^-1.The excellent SERS sensitivity of this waffle-shaped AAO/Ag substrate is attributed to the formation of many hot spots of Ag NPs on its surface,and the target sample can better aggregate in the short-hole AAO near the hot spot compared to the long-hole AAO.In practical applications,that is,for the rapid detection of chloramphenicol?CAP?in honey,the spiked recovery range is 96%-106%.In addition,SERS substrate is highly selective and can separate CAP from its analogs due to the high interaction between the NO₂groups in the CAP and the substrate.2.In-situ synthesis of Ag NPs is simple and easy-to-operate,yet its reproducibility still needs to be enhanced.Therefore,in Chapter 3,Ag NPs are first synthesized then assembled into AAO nanopores by ultrasonication.The successful fabrication of Ag NPs and AAO@Ag SERS substrates are characterized via Ultraviolet?UV?and SEM.Such SERS substrate has superior stability,i.e.the SERS activity still retains 75%of the original substrate after 60 days exposure in air at room temperature.The LOD of enrofloxacin is 7.2×10^-9mol?L^-1,and the linear range is 10^-4mol?L^-11 to 10^-88 mol?L^-1?R²=0.9645?.The minimum detection concentration in the real sample,milk,is 2.8×10^-88 mol?L^-1,and the recovery rate is 92%-104.2%.3.The above two works focus on the selectivity,uniformity and stability of the substrate,leaves the sensitivity to be further improved.The work in Chapter 4 is therefore aimed at addressing substrate sensitivity.The Au NPs are sputtered to the bottom of the AAO.Through optimization of the sputtering time,a highly sensitive AAO@Au SERS substrate is successfully prepared.For R6G probe molecules,the substrate has a low detection limit of 10^-1010 mol?L^-11 and good reproducibility?RSD=4.78%?.The LOD of fipronil is 1.9×10^-9mol?L^-1,and it has a good linear relationship between 10^-44 mol?L^-11 and 10^-77 mol?L^-1.R²=0.9710.The minimum concentration of 9.2×10^-99 mol?L^-11 in the detection of eggs in real samples was spiked.The recoveries of spiked samples are 87.5%-107.5%.